Semiconductor chips are used in a very wide variety of ways. In this case, they have, if it is not an individual component, for example a transistor, a more or less complex integrated circuit on their surface. In principle, the invention described later is independent of the complexity of the integrated circuit, with the result that a semiconductor chip having an individual component, for example a transistor, may also ultimately be involved below. However, for the purpose of simplification, an integrated circuit on one surface of the semiconductor chip will be assumed below. However, this is not intended to exclude the fact that it could also be an individual component.
In the past, the semiconductor chip was placed in a housing, for which purpose that side of the semiconductor chip which faced away from the integrated circuit was frequently placed on a carrier, and contacts, which are part of the integrated circuit, were connected, for example by means of wire bonding connections, to contacts of the carrier which are used as connections of the housed component. However, a housed component of this type is not suitable in some areas. For many years, integrated circuits have been produced on semiconductor chips which are arranged in plastic carriers in the form of cards. In this respect, mention may be made, by way of example, of the so-called “SIM” card which is intended for use in a so-called mobile phone or else the health insurance card which is widely used at least in Germany. In applications of this type, it is understandable that, in the case of the desired minimal thicknesses, a conventional housing is not provided. For this reason, it has been known practice, for a long time, to produce a so-called chip module which comprises, for example, a plastic carrier which has the “ISO” contacts which are known from the “SIM” card on one side, for example. In the case of the known arrangements, that side of the semiconductor chip which faces away from the area in which the integrated circuit is formed is placed and fastened on that side of the carrier which is opposite the contacts. The contacts on the semiconductor chip which are connected to the integrated circuit are electrically conductively produced, by means of a wire bonding connection, to form pads on the carrier, which are, in turn, connected to the abovementioned contact areas. These wire bonding connections are sensitive and were therefore frequently covered. As can be discerned, a procedure of this type has a large number of production steps which, in turn, contradict the usual obligation to produce chip modules of this type in a cost-effective manner. For the purpose of simplification, it has likewise become known practice in the meantime to produce chip modules of this type such that the semiconductor chip is electrically conductively placed on the carrier and connected using so-called flip-chip technology. To this end, contact elements, so-called “bumps”, are first of all produced on the surface of the semiconductor chip, said contact elements being intended to produce an electrically conductive connection between the contact areas of the integrated circuit and corresponding contact areas on the substrate. In order to ensure this, a soldered connection to these bumps is produced.
An arrangement of this type is illustrated, by way of example, in FIG. 5. A semiconductor chip 1 has an integrated circuit 1a in the region of its surface 2. Said integrated circuit is covered by a chip passivation 4, the chip passivation 4 having bushings through which contact elements 3 for contact-connecting the integrated circuit 1a are formed. In order to form these contact elements 3, contact areas (not illustrated) of the integrated circuit 1a are provided with a metallic layer on the surface 2. In this case, a nickel layer which is deposited on the outside without using electric current is preferably applied. This process causes all of the metal areas on the chip to be coated with nickel. Since metal areas are usually situated in the edge region of the semiconductor chip, the so-called scribing frame or sawing frame, they are also coated with nickel. Coating of this type is undesirable. It can also be seen in FIG. 5 that the contact elements 3 of the semiconductor chip 1 are arranged on a substrate or carrier 9. The latter has conductor structures on the side 10 facing the semiconductor chip 1 and is, overall, in the form of a so-called “leadframe”. When the semiconductor chip 1 is being placed on the substrate 9 and the contact elements 3 are being soldered to contact areas opposite, the substrate 9 is regularly bent, with the result that its surface 10 comes to rest on the surface 2 of the semiconductor chip 1. From time to time, this results in disturbances, for example leakage currents or short circuits.